我在执行this查询时在Windows上使用PostgreSQL 9.2：
SELECT
gtab16.VrId,
coalesce((
select (gtab09.TdAmt+gtab09.CdAmt)
from gtab09
Where gtab09.JrmId = gtab16.JrmId
limit 1
), 0::money
) as DisAmount,
gtab02.VrName,
gtab02.Vrlongname,
gtab16.AcYrId,
CASE WHEN gtab16.vrid = 28 THEN gtab16.RefNo ELSE gtab16.VrNo END AS VrNo,
gtab16.RefNo,
CASE
WHEN gtab16.VrId = 10 THEN cast((
Select coalesce(PBillDate,null)
from gtab09
Where gtab09.JrmId = gtab16.JrmId
) as bpchar)
ELSE ''
END As BillDate ,
Cast(gtab16.VrDate As timestamp) As VrDate,
gtab16.AgeDate,
(
SELECT coalesce(Sum(gtab18.ageamt),0::money)
FROM
(gtab16 AS A INNER JOIN gtab17 AS B ON A.jrmId = B.JrmId)
INNER JOIN
gtab18 ON B.JrDetId = gtab18.crjrdetid
WHERE gtab18.drjrdetid = Gtab17.JrDetId AND A.AgeDate <= '2014-07-09'
) AS AgedAmt,
case when gtab17.dr > 0::money then gtab17.Dr else gtab17.Cr end AS VrAmt,
gtab17.AcId, gtab12.AcName,
gtab12.AcShortName,
gtab12.PhoneOff,
case when gtab17.cr > 0::money then 1 else 0 end AS Receipt,
gtab47.AreaName,
gtab16.JrMId,
gtab17.JrDetId,
date_part('day','2014-07-09' - Gtab16.agedate) as DayCount,
(
SELECT coalesce(sum(chqAmt),0::money)
From gtab19
Where PartyAcId = gtab17.acid and vrid = 19 And Pdc =1
) as PDCCheq,
30 As Span1,
60 As Span2,
90 As Span3
FROM
(
gtab16
INNER JOIN
(
gtab17
INNER JOIN
gtab12 ON gtab17.AcId = gtab12.acid
) ON gtab16.jrmId = gtab17.JrmId
)
INNER JOIN gtab02 ON gtab16.VrId = gtab02.vrId
INNER JOIN gtab47 ON gtab12.AreaId = gtab47.AreaId
WHERE
gtab16.BranchID = 1 And
gtab17.Dr > 0::money AND
case when gtab16.AcYrid = 2 then 1 else gtab16.VrId end <> 6 And
date_part('day','2014-07-09' - Gtab16.agedate) >= 0 AND
(gtab12.AcGrCode = '204' or gtab12.AcGrCode = '103') And
gtab47.AreaId IN (7) AND
date_part('day', '2014-07-09' - gtab16.AgeDate) >= 0 And
(gtab17.Dr - (
SELECT coalesce(Sum(gtab18.ageamt),0::money)
From
(
gtab16 AS A
INNER JOIN gtab17 AS B ON A.jrmId = B.JrmId
)
INNER JOIN gtab18 ON B.JrDetId = gtab18.crjrdetid
Where
gtab18.drjrdetid = Gtab17.JrDetId AND
A.AgeDate <= '2014-07-09') > 0::money
) AND
gtab16.VrDate Between '2014-07-01' And '2014-07-09'
需要很长时间，here是explain analyze：
"Nested Loop (cost=0.00..98913858.59 rows=9 width=363) (actual time=302403.378..302628.382 rows=71 loops=1)"
" -> Seq Scan on gtab47 (cost=0.00..1.30 rows=1 width=122) (actual time=0.006..0.010 rows=1 loops=1)"
" Filter: (areaid = 7)"
" Rows Removed by Filter: 23"
" -> Nested Loop (cost=0.00..98908508.69 rows=9 width=249) (actual time=302400.148..302405.795 rows=71 loops=1)"
" Join Filter: (gtab16.vrid = gtab02.vrid)"
" Rows Removed by Join Filter: 3834"
" -> Seq Scan on gtab02 (cost=0.00..1.55 rows=55 width=150) (actual time=0.004..0.052 rows=55 loops=1)"
" -> Materialize (cost=0.00..98908499.74 rows=9 width=103) (actual time=5380.762..5498.218 rows=71 loops=55)"
" -> Nested Loop (cost=0.00..98908499.70 rows=9 width=103) (actual time=295941.855..302398.524 rows=71 loops=1)"
" Join Filter: (gtab17.jrmid = gtab16.jrmid)"
" Rows Removed by Join Filter: 1886191"
" -> Nested Loop (cost=0.00..98897543.98 rows=2015 width=69) (actual time=7.437..299102.826 rows=2037 loops=1)"
" Join Filter: (gtab17.acid = gtab12.acid)"
" Rows Removed by Join Filter: 12893055"
" -> Seq Scan on gtab17 (cost=0.00..98819605.03 rows=29138 width=28) (actual time=2.974..276230.715 rows=68228 loops=1)"
" Filter: ((dr > (0)::money) AND ((dr - (SubPlan 5)) > (0)::money))"
" Rows Removed by Filter: 111761"
" SubPlan 5"
" -> Aggregate (cost=548.98..549.00 rows=1 width=8) (actual time=3.131..3.132 rows=1 loops=88001)"
" -> Nested Loop (cost=0.71..548.98 rows=1 width=8) (actual time=2.707..3.126 rows=0 loops=88001)"
" -> Nested Loop (cost=0.42..548.64 rows=1 width=12) (actual time=2.701..3.119 rows=0 loops=88001)"
" -> Seq Scan on gtab18 gtab18_1 (cost=0.00..540.19 rows=1 width=12) (actual time=2.693..3.109 rows=0 loops=88001)"
" Filter: (drjrdetid = gtab17.jrdetid)"
" Rows Removed by Filter: 28575"
" -> Index Scan using gtab17_pkey on gtab17 b_1 (cost=0.42..8.44 rows=1 width=8) (actual time=0.005..0.006 rows=1 loops=28574)"
" Index Cond: (jrdetid = gtab18_1.crjrdetid)"
" -> Index Scan using gtab16_pkey on gtab16 a_1 (cost=0.29..0.33 rows=1 width=4) (actual time=0.004..0.005 rows=1 loops=28574)"
" Index Cond: (jrmid = b_1.jrmid)"
" Filter: (agedate <= '2014-07-09 00:00:00'::timestamp without time zone)"
" -> Materialize (cost=0.00..140.94 rows=178 width=45) (actual time=0.001..0.160 rows=189 loops=68228)"
" -> Seq Scan on gtab12 (cost=0.00..140.05 rows=178 width=45) (actual time=0.057..0.927 rows=189 loops=1)"
" Filter: ((areaid = 7) AND (((acgrcode)::text = '204'::text) OR ((acgrcode)::text = '103'::text)))"
" Rows Removed by Filter: 2385"
" -> Materialize (cost=0.00..3037.42 rows=262 width=38) (actual time=0.006..0.788 rows=926 loops=2037)"
" -> Seq Scan on gtab16 (cost=0.00..3036.11 rows=262 width=38) (actual time=10.342..13.037 rows=926 loops=1)"
" Filter: ((vrdate >= '2014-07-01 00:00:00'::timestamp without time zone) AND (vrdate <= '2014-07-09 00:00:00'::timestamp without time zone) AND (branchid = 1) AND (CASE WHEN (acyrid = 2) THEN 1 ELSE vrid END <> 6) AND (date_p (...)"
" Rows Removed by Filter: 58837"
" SubPlan 1"
" -> Limit (cost=0.29..8.31 rows=1 width=16) (actual time=0.011..0.012 rows=1 loops=71)"
" -> Index Scan using gtab09_jrmid_idx on gtab09 (cost=0.29..8.31 rows=1 width=16) (actual time=0.007..0.007 rows=1 loops=71)"
" Index Cond: (jrmid = gtab16.jrmid)"
" SubPlan 2"
" -> Index Scan using gtab09_jrmid_idx on gtab09 gtab09_1 (cost=0.29..8.31 rows=1 width=8) (never executed)"
" Index Cond: (jrmid = gtab16.jrmid)"
" SubPlan 3"
" -> Aggregate (cost=548.98..549.00 rows=1 width=8) (actual time=2.975..2.975 rows=1 loops=71)"
" -> Nested Loop (cost=0.71..548.98 rows=1 width=8) (actual time=2.968..2.970 rows=0 loops=71)"
" -> Nested Loop (cost=0.42..548.64 rows=1 width=12) (actual time=2.965..2.966 rows=0 loops=71)"
" -> Seq Scan on gtab18 (cost=0.00..540.19 rows=1 width=12) (actual time=2.959..2.960 rows=0 loops=71)"
" Filter: (drjrdetid = gtab17.jrdetid)"
" Rows Removed by Filter: 28575"
" -> Index Scan using gtab17_pkey on gtab17 b (cost=0.42..8.44 rows=1 width=8) (actual time=0.005..0.006 rows=1 loops=1)"
" Index Cond: (jrdetid = gtab18.crjrdetid)"
" -> Index Scan using gtab16_pkey on gtab16 a (cost=0.29..0.33 rows=1 width=4) (actual time=0.007..0.009 rows=1 loops=1)"
" Index Cond: (jrmid = b.jrmid)"
" Filter: (agedate <= '2014-07-09 00:00:00'::timestamp without time zone)"
" SubPlan 4"
" -> Aggregate (cost=28.63..28.64 rows=1 width=8) (actual time=0.130..0.131 rows=1 loops=71)"
" -> Seq Scan on gtab19 (cost=0.00..28.62 rows=1 width=8) (actual time=0.124..0.124 rows=0 loops=71)"
" Filter: ((partyacid = gtab17.acid) AND (vrid = 19) AND (pdc = 1))"
" Rows Removed by Filter: 607"
"Total runtime: 302628.704 ms"
PostgreSQL服务器端config max_connections 10000
max_stack_depth 2MB
shared_buffers 1GB
temp_buffers 1GB
是新的，所以我们非常感谢任何建议或建议
答案 0 :(得分：0)
，您会看到查询速度慢的地方。
但在进行查询优化之前，请阅读有关它的教程以了解什么是seqscan / loop / cast等...并且请尝试重写您的查询以使其更简单！我想你可以。
阅读@wildplasser所说的内容，因为Select coalesce(PBillDate,null) from是由于合并使用不全面...... Select PBillDate from是相同的，所以不需要进行必要的治疗。
但是为了帮助你，当我在这种情况下，我尝试删除所有select子句以仅保留一个并删除对于我的select子句不必要的连接并播放查询。尝试使用正确的连接逐个重新添加select子句，如果你看到你的查询时间在增长，请做一个解释，转到depesz网站阅读解释并尝试检测你的查询速度慢的地方并添加索引或重写它
很难阅读大型查询并尝试对其进行优化，因此请逐步添加select子句，您将找到解决方案。
并检查您的统计数据是否正常，否则您的解释将不正确。你可以做真空来刷新你的数据。并尝试explain analyze而不是explain，因为explain analyze播放了真实的查询并返回了许多其他信息，以查看每个部分的费用。
阅读解释分析教程，因为你有很多选项非常有用;）
祝你好运